Furnace regulating system



Dec. 5, 1933. D. J. STEWART 1,937,601

FURNACE REGULAT I NG SYSTEM Filed April 11, 1932 TO LINE IIIIIBi' IIIIIIIIIIIIIIIIIIE|H lllllllllllllllllllllllllllllllllllllll & 2 f s -I g I w 1% 2 i Q lf .gk T 66 6 64 g 65 INVENTOR I 7 Duncan J. Stewart WMv IIIWIIIIII ATTORNEYS Ill v///////////////// Patented Dec. 5, 1933- UNITED j STATES 1,937,601 7 FURNACE REGULATING SYSTEM Duncan J. Stewart, Rockford, 111., assignor Howard D. Colman, Rockford, 111.

Application April 11, 1932. 1 Serial o. 604,467

15 Claims. (01. 23616) This invention relates to the actuation of the.

regulating dampers of :a furnacefor a heating system and more particularly to a system in which the dampers are actuated by a power operator controlled by a thermostat located in the space heated'by the furnace.

Modern furnaces for burning solid fuel are commonly regulated by socalled draft and check.

dampers arranged to be moved under thermostatic control between a heat-increasing position in which the draft damper is open and the check damper closed and a heat-decreasing position in which the positions of these dampers are-reversed. During firing of such afurnace, it is desirable that the check dampers be closed in order to create as great a draft aspossible and also that the draft damper be closed in order that the entire draft will be effective in causing air to flow into the firing door of the furnace, thereby preventing smoke and dust from being discharged out of the firing door.

One object of the present invention is to provide new and improved control for furnace regulators by which the power operator normally employed for actuating the check and draft dampers of the furnace is also usedto move the devices to a firing position in which both'of said dampers are closed.

Another object is to provide an electrically driven furnace regulator having an actuating element driven between heat-increasing and heat-decreasing positions under the control of a thermostat and anormally controllable means by which the electric driving means of said regulator is withdrawn from the control of the thermostat and started in operation toadvance said element to a firing position.

A further object is to combine with a control system of the above character a novel means for .restoring the furnace regulator to the normal control of the thermostat after the lapse of a predetermined interval allotted for firing of the furnace. v

The invention also resides in the novel character of the switching mechanism by which the movements of the actuating element are defined and the thermostat rendered effectual and ineffectual in its control over the power operator of the regulator.

Other objects and advantages of the invention will become apparent from the following detailed trolled by a regulating system embodying the features of the present invention. I

Fig. 2 ,is a plan view of a timing device which may be used in the present system, the casing. of the device being shown in section;

Figs. 3 and 4 are sectional views taken respectively along the lines 33 and 4-4 of Fig. 2.

In the drawing, the numeral 5 indicates a furnace adaptedto burn solid fuel andto deliver.. varying amounts of heat to a space to be heated according to the positions of draftand check dampers 6 and 7. The latter are moved simulta'-;

neously in opposite directions'inthe movement of an actuating element in the, form of a shaft S'carrying the usual oppositely extending cranks 9 connected respectively to the dampers 6 and 7 by cords it. When the shaft is positioned as shown in Fig. l, the draft damper 6 is open and the check damper is closed thereby allowing combustion to occur at-a maximum rate. Rotation of the'shaft through a half revolution to a position, hereinafter referred. to as the heat-de creasing position, causes closure of the draft damper 6 and opening of the damper '7 withthe result that combustion is checked. Sufficient slack is allowed in each cord 10 when the associ f ted damper is closed to permit such damper to remain closed-for the subsequent quarter revolution of the shaft. Thus by movementgof the shaft clockwise through a quarter revolution from the 35 position shown in Fig. l, the shaft will be brought to a position in which both of the dampers 6 and "7 are closedand the furnace thereby conditioned for firing. Thislatter position will be referred to asthe firing position.

The power operator shown in the drawing. for actuating theshaft 8 comprises asmall fractional horse power motor 11 having a rotary shaft 12 connected to the shaft 8 through a train 13 of speed reduction gears. The motor operates'unidirectionally whenever its winding 14 is. ener gized from a source 15 of alternating current tov one terminal of which the windingis connected as indicated in Fig. 1 by grounding. V The normal'operation of the motor to define operating cycles of fixed length; inwhich the. shaft is moved through half revolutions alternately to heat-increasing and heatsdecreasing positions, is underthe joint control of-a thermo stat 15 and a mechanically operated switch mechanism associated with the motor unit. The thermostat may comprise atherm o-sensitive element 16 having a tongue 17 carrying a common* contact of two switches 13 and 19 which are p 7 closed respectively when the temperature in the space heated by the furnace rises above and falls below the temperature for which the thermostat is set to respond.

Preferably, the switch mechanism above re.- ferred to is associated with the motor unit and comprises three switches 23, 21 and 22 respectively controlling two starting circuits for initiating the normal cycles of the motor operator and a maintaining circuit determining the length of these cycles. Each switch has a movable contact on the end of a spring. arm 23 connected by a conductor 24 to the winding 14. Movement of the arms 23 relative to the stationary contacts of. the switches is controlled by cams 25, 26 and 2'7 fast on a shaft 28 driven through gears 29 at the same speed as the shaft 8.

The two starting circuits include a common conductor 30 extending between the current source 15 and the common contact of the ther mostat switches and having interposed therein a normally closed switch 31 and a second switch normally closed by engagement of an arm 32 with a contact 33. To complete the above starting circuits, the stationary contacts of the switches 18 and 19 are connected respectively to the stationary contacts of the switches 20 and 21 by conductors 34 and 35. The maintaining circuit includes a conductor 36, extending from the stationary contact of the switch 22 to the current source.

The cam 26 is constructed with a notch 37 which allows the switch 21 to open before the shaft 8 reaches heat-increasing position (see Fig. l) the switch being closed, for a purpose to appear later, before the shaft 8 reaches the firing position above referred to. In a similar way, the cam. 25 is formed with a notch 38 whichallows the switch to open only when the shaft 8 is near or at heatdecreasing position. Notches 39, 40 and 41 in the earn 2'? allow the maintaining circuit to open when the shaft 3 reaches heat-increasing, firing and heat-decreasing positions respectively.

The normal operation of the furnace regulator above described is as follows, assuming the parts I through a half revolution, the switch 22 is opened thereby terminating the cycle with the check damper open and the draft damper closed, the

to be positioned as shown in Fig. 1 When'the ethermostat ceases to call for heat, closure of the switch 20 having been opened and the switch 21 closed. Now when the thermostat calls for heat, closure of the switch 19 will complete a starting circuit throughthe switch 21 initiating operation of the motor which will be continued until the shaft 8 has reached the position shown in Fig. 1 whereupon the motor will be deenergized.

.Manually controllable means is provided for withdrawing the motor from the control of .the thermostat and causing a cycle of the motor to be initiated for advancing the shaft'8 to firing position preparatory to firing of the furnace. In thepresent instance, the thermostat is rendered ineffectual by interposing a gap in the conductor 30 and independent operationof the motor is initiated by establishing a separate starting circ,uit-iorthe motor through a switch 42 having a closure of a switch 48 interposed in a conductor 49 between the current source 15 and the conductor 47. With the shaft 8 in either of its normal respective positions, it will be apparent that upon closure of the switch 48 or of the switch 32, 46, the motor winding will be energized through the independent circuit including the then closed switch 42 and will continue in operation until the firing position is reached whereupon the motor will be deenergized due to entry of the followers of the cams 2'7 and 44 into the notches 40 and 45, the starting circuits controlled by the ther- .mostat switches then being broken either at the contact 33 or by the switch 31 as willlater appear.

As in the case of the switches 32, 33and 32, 46,

the switches 31 and 48'preferably are arranged vto be actuated by a cam element herein shown as a bell crank lever 50 pivoted at 51 and having an arm 52 abutting one end of a coiled compres-' sion spring 53, the other end of which engages the closed end of a U-shaped arm 63 loosely pivoted at 51. The arm 63 enters a slot in a plate 54 rigid with a bell crank 55' carrying the movable contacts of the switches 31 and 43. By moving the lever 56 downwardly from the position'shown in Fig. 3, the bell crank 55 is moved with a snap 7 action to its other limit position in'whichthe stationary contact is engaged.

The independent circuit for initiating operation of the motor to advance the shaft 8 to. firing position may be. rendered inefiectual and the eontrol of the motor restored to the thermostat 15 by manual operation which may be effected convenlently by moving the contact arm 32 from the contact 46 to the contact 33. It is preferred, however, to effect such restoration of thetthermostat control automatically after the lapse of an interval of sufficient duration to allow for normalfiring of the furnace. For this purpose a timing device may be employed which operates independently of the motor operator to .hold the switch 48 closed and the switch 31 open for a predetermined interval and then to reverse the conditionsof these switches. Y 7

The timingdevice selected for illustration includes a clockwork 58 driven by a'main spring 59 wound to apredet'ermined degree by advancement of a pawl 60 into engagementwith a reset .wheel'fileachtime the lever 50 is lowered.v Such movement of the lever moves the spring 53 over. center with respect to the bell crank pivot 62v causing the bell crank 55 to be thrown from the position shown in Fig.3 to a position in which the switch 48 is closed. In this movement, the arm 63 is lowered allowing a pivotal latch 34 to move under the influence of a spring 65 to'a position where an offsetlug66 on thelatch'overlies the free end of the arm 63 preventing upwardmovement of the arm when thelever 50 is again raised to the position shown in Fig. 3.

Winding of thespring 59 as above described starts theclockvrork in operation causing an arm 67 on :a slow speed member of the gear train to rotate in a clockwise direction. When the spring becomes substantially unwound, the arm 67 engages a cam surface 68 on the latch 64 withdrawing the latter until the lug 66 passes out of engagement with the arm 63 thereby allowing the latter to be moved by the: spring 53 into the position shown in Fig. 3. The-switch 48 is thereby opened and the switch 31 closed, the latter serving to reconnect the thermostat tongue to the current source. i 3

With the timing device above described, it

will be apparent that the duration of the. in-.

terval allotted for firing of the furnace is goverened by the extent to which the spring 59 is wound up. To increase this interval, it is merely necessary to actuate the lever more than once, each additional actuation increasing the tension on the spring to a predetermined degree thereby prolonging the interval during which the dampers are held in firing position.

Upon closure of the switch 31 and simultaneous opening of the switch 48 or upon movement of the contact arm 32 from the contact 46 to'the contact 33, it will be apparent that the motor operator is restored to the exclusive control of the thermostat with the resultthat the motor will be started and the shaft .8 moved to a heatincreasing or-heat-decreasing position depending on which of the thermostat switches 18, and 19 is closed at the time. This is made possible'by constructing the cams 25 and ,26 in such away that both of the switches 20 and 21 will be closed when the shaft 8 is in firing position.' Thus if the switch 19 is closed when the thermostat is rendered effectual, a starting circuit will be completed through the switch 21 and the motor will be started and continue to operate under the control of the maintaining circuit until the heatincreasing position of the shaft 3 is reached. In this operation the starting circuit through the switch 21 maintains the motor circuit whilethe switch 22 is open as the notch 41 is presented to the follower of the cam 27.

From the foregoing it will be apparent that a simple and inexpensive control system has been provided for utilizing the motor of a furnace regulator to move the actuating element for the dampers to a firing position, the latter being accurately defined by the switch mechanism which is actuated in accordance with movements of the shaft 8. g The use of clutches for enabling the motor and shaft 8 to be disconnected preparatory to firing is avoided. The construction is simple and inexpensive and lends itself readily to restoration of the thermostat control either manually or automatically as desired, the timing device being operated from the furnace regulator proper.

I claim as my invention:

1. In combination with a furnace having check and draft dampers, an actuating element connected to said dampers and having a position in which said check and-draft dampers are open and closed respectively, a second positionin which said check and draft dampers are closed and opened respectively and an intermediate position in which both of said dampers are closed, an electric motor for driving said element, a thermo stat normally controlling said'motor to initiate movement of said element into said first and second mentioned positions respectively when the temperature in the space heated by said furnace rises above and falls below-a predeter-.

mined value, switching means controlled in accordance with the movement of said elementto terminate the operation of said-motor when the element reaches said first or second positions in response to control by said thermostat, manually controllable switching means for withdrawing said thermostat from the control of said motor and initiating operation of the latterto move said element toward said intermediate position, and switching means controlled in accordance with the movements of said element and operable, upon starting of said motor by said manually controllable switching means, to terminate the operation of the motor With said'elernentv in said intermediate position. T v

2. In combination with a furnace'having'check J and draft dampers, an actuating.element'connected to said dampers and having a position in which said check and draft dampers are open and closed respectively, a second position'in which said checkand draft dampers are closed and opened respectively and an intermediate position in which both of saiddampers are closed, an electric motor for driving said element, a'source of said'check and draft dampersare closed and,

opened respectively and an intermediate position in which both of said dampers are close'd,g-an electric motor for driving said element, two thermostat switches each controlling the closure of an energizing circuitfor said motor,'a switch controlling the closure of an independent energiz ing circuit for said motor, manually operable means for closing said last'mentioned means and interrupting said first mentioned'circuits independently of said thermostat, and switching means operated in acco rdance with'the movements of said element to interrupt the operation electric-current, fitwo thermostat switchesptwo. Y

of said motor with said element insaid'first mentioned positionfollowing closure of one of said first mentioned circuits, in said second position following closureof the other thermostatically controlled circuit and in said intermediate position following closure of said independent circuit.

4. In combination with a furnace havingjche ck and draft dampers, an actuating element connected to said dampers and having a position in I which said check and draft dampers are'open and closed respectively, a second position in which.

said check and draft dampers areclosed and T openedrespectively and an intermediate position in which both of said dampers are closed, "an

electric motor for driving said element, a source 1 of electric current, two thermostat switches, two

energizing circuits for said motorhaving a conductor'extending between said current source and a common terminal of saidswitches, aswitch in in either of said first mentioned positions, and a manually operable actuator for said la-st-menpendent circuit upon opening".v and closure o'fthe "5. In combination with a" furnace having a plurality of controlling regulators, an actuating said conductor, an independent circuit for jsaid' motor adapted to be closedwhen said element is .145- j r tioned switch adapted to close andopensaid indeelement connected to said regulators and mov-' able through heat-increasing, heat-decreasing and firing positions, an electric motor for driving said element, a thermostat normally controlling said motor to initiate movement or" said element away from one of said first mentioned positions to the other position, switchingmeans controlled by the movements of said element and operable to interrupt operation of said motor when said element has reached said last mentioned position, manually controllable means for rendering said thermostat ineffectual and for initiating operation of said motor to move said element from either of said first mentioned positions toward said firing position, and means controlled by the movements of said element and I operable to interrupt the operation of said motor when said element reaches said firing position with said thermostat ineffectual.

; switches each controlling one of said thermostat circuits, and means controlled by the movements of said elementand operable to maintain one of said switches closed and the other open while saidelement is in each or" said limiting positions and both of said switches closed when 'said element is in said third position.

'7. In combination with a furnace having a plurality of controlling regulators, an actuating element connected to said regulators and movable between heat-increasing and heat-decreasing positions through a firing position, an electric motor for driving said element, a thermostat normally controlling said motor to cause move ment of said element from one of said first men tioned positions to the other, and manually controllable switching means adapted, when rendered active, to cause movement of said element by said motor to saidfiring position. v

8. In combination with a furnace having a plurality of controlling regulators, an actuating element connected to said regulators and movable through heat-increasing, heat-decreasing and firing positions, an electric motor. for driving said element, a'thermostat normally controlling said motor to cause movement of said element from one of said first mentioned positions to the other, and manually controllable means for rendering said thermostat inefifectual and for initiating independent operation of saidinotor to move said element to said firing position.

9; In combination with a damper actuating element, power-driving means for said element,

thermostatic means normally controllingsaid driving means to cause movement of said element from one predetermined position to another,

and manually operable means controlling said driving means to cause said element to be advanced' to and stopped in a third position.

' 10. In combination with a furnace having check and draft dampers, an actuating element connected to said dampers and-having aposition in which said check and draft dampers are open and closed respectively, a second position in which said check and draft dampers are closed .and opened respectively andan intermediate position in which both of said dampers are closed, an electric motor fordrivingsaid element, a source of electric current, two thermo stat switches, two energizing circuits for-said motor having a conductor extending between said current source and a common terminal of said switches, an independent circuit through which said'mo-tor may be energized whensaid element is in either of said first mentioned posi'-' tions, manually operable switching means for interposing a gap in said conductor and establishing said independent circuit, and means operable automatically after the lapse of a predetermined interval allotted for firing of said furnace to close said gap and interrupt said independent circuit.

11. In combination with a furnace having a plurality of controlling regulators, an actuatingelement connected to said regulators andmovable between heat-increasing and heat-decreasing positions through a firing position, .an electric motor for driving said element, a thermostat normally controlling said motor to initiate movement of said element away from one of said first mentioned positions to the other position, switching means controlled by the movements of said element'and operable to interrupt operation of said motor'when said element has reached said last mentionedposition, manually. controllable means for rendering said thermostat ineffectual and for initiating operation of said motor to move said element from either of saidfirst mentioned positions toward said firing position, switching means controlled by the'movement of said element and operable to interrupt the opera tion of said motor when said element reaches firing position with said thermostat ineffectual, and means operable automatically after the lapse of a predetermined firing interval to interrupt said independent circuit and restore said motor to the control of said thermostat.

12. In combination with a furnace having a regulator, an element for actuating said regulator movable between heat-increasing andheatdecreasing positions through an intermediate firing position, an electric motor arranged to drive saidelement, thermostatically controlledswitching means normally governing the operation of said motor to move said element between said first mentioned positions, manually controllable switching means for rendering said last mentioned switching means ineffectual and causing operation of said motor to move saidelement-to said firing position, and a timing device set in operation as an incident to operation ofsaid manually controllable switching means and operable after the lapse of a predetermined'time interval to restore said motor to the exclusive'control of said thermostatically controlled switching means.

13. In combination with a furnace having a plurality of controlling regulators, an'actuating' elementconnected to said regulators and movable between heat-increasing and heat-decreas ing positionsthrough a firing position, an electric motor for driving said element, a thermostat normally controlling said motor to cause movement of said element from one of said first mentioned positions to the other, manually controllable means for causingoperation of said motor to ad- Vance. said element to'firing position and thereafter maintaining the motor at rest, and means operable automatically after the lapse of a predetermined interval for firing o f said furnace to recally after a lapse of time to place said driving means Within the exclusive control of said thermostatic means.

15. In a temperature control system, the combination of a control element to be moved into thermostat.

any one of three different positions, power driv ing means for said element, thermostatic means normally controlling said driving means to cause movement of said element from one of said positions to another and vice versa, auxiliary control means by which said driving means may be controlled to cause movement of saidelement to the third position independently of said thermostatic means, and means acting automatically after said element has been positioned in said third position for a predetermined time interval to render said auxiliary control means ineffectual and restore said driving means to the control of the DUNCAN J. STEWART. 

